1. Field of the Invention
The invention relates to the field of dithered ring laser gyroscopes, and more particularly to apparatus for reducing the vibrations of the mounting plate induced by dithering the ring laser gyroscope.
2. Description of the Prior Art
A ring laser gyroscope utilizes two monochromatic laser beams propagating in opposite directions in a closed loop around an axis about which motion is to be sensed. Rotation of the apparatus about this axis effectively increases the beam path length in one direction and decreases the beam path length in the opposite direction. Since the laser frequencies of the two counter-rotating beams are functions of the lasing path, the differential path length established by the rotation of the ring laser gyros establishes a frequency difference between these beams. The magnitude and sign of this frequency difference are representative of the rate and direction of rotation about the sensing axis and may be monitored for that purpose in manners well known in the art. At low rotational rates, the difference in frequency between the two counter-rotating beams is small and the beams tend to resonate together or "lock-in" to oscillate at the same frequency. This lock-in prevents the ring laser gyroscope from sensing rotational rates that are at or below the lock-in rotational rate. To reduce the lock-in rate, the ring laser gyroscope is dithered, mechanically oscillated about the axis to establish rotation in one direction and then in the other, to provide motion cancellation at the output terminals while maintaining an apparent rotation in each direction, thus reducing the lock-in rate.
This dithering causes the ring laser gyroscope mounts to vibrate thereby, acting as a noise generator which adversely affects other equipment. Though well known techniques for vibration, damping, and isolation reduce the dither generated vibrations, the degree of vibration reduction is insufficient to prevent an adverse affect upon other equipment vibration coupled to the ring laser gyro mounting plate.